Centrifuges and other equipment for separating particles in suspension operate by spinning tubes or other containers containing the suspension at high angular rotational speeds. Centrifugation is common in medical testing, purification of samples, and other such endeavors. The high speeds of revolution in a centrifugation process are typically in the range of 2700 revolutions per minute (RPM) and higher. In order to accomplish such high speeds of revolution, it is necessary to use high speed motors and special precision equipment.
When multiple samples are placed in a centrifuge, each must be labeled carefully, because the high rotational speeds and the sheer number of rotations that the centrifuge contents undergo makes it very difficult to stop rotation of the centrifuge bucket exactly where it started. Typically, when multiple samples are placed into a centrifuge, each sample is labeled or coded, and placed individually by a technician or other operator into the centrifuge. After completion of the centrifuging operation, the samples are typically removed, again by a technician or other operator, identified by the labeling, and cataloged, stored, or used accordingly.
Recently, an automated procedure and apparatus allowing for robotic placement of multiple samples into a centrifuge was disclosed in greater detail in co-owned U.S. patent application Ser. No. 09/420,965, assigned to the assignee of the present application, which is herein incorporated by reference in its entirety. Operation of such an apparatus may be controlled by use of a computer-control system such as those disclosed in co-owned U.S. patent application Ser. Nos. 09/255,146 and 09/361,829, which are also herein incorporated by reference in their entirety. Such procedures and apparatuses place samples into centrifuging stations or centrifuges for operation of certain separating processes performed by the centrifuges.
Rotors of typical centrifuges, because of their extremely high speeds of rotation, typically xe2x80x9cfloatxe2x80x9d in an approximate circular pattern while they rotate. The rotation is driven by a belt drive connected to a motor off to the side of the centrifuge bucket. The rotor shaft operates through the use of a special bearing assembly which allows the rotor shaft to float, which in turn allows for out of balance rotation, or unbalanced loads in the centrifuge bucket. In other words, the axis of rotation of the rotor shaft is not closely constrained. When the centrifuge rotation is slowing down and eventually stops, there is generally no reliable method for determining without visual confirmation the angular position of the bucket. Therefore, samples placed in the centrifuge are difficult to remove with an automated process, without further analysis of the samples, such as reading bar codes or the like.
When using an automated process for placing samples in a centrifuge bucket, and an automated process for removing the samples when centrifugation is complete, it would be desirable to allow for removal of the samples in the order in which they were placed in the centrifuge, or in reverse order. It would also be desirable to be able to remove samples without the need for supervision by a technician or operator of the equipment.
Further, when samples are placed in a centrifuge bucket, they may be placed in such a position that the centrifuge bucket is unbalanced, and rocks off its gravitational center. In such a situation, an automated process for removing samples, which need to be precise for correct operation, may have difficulty aligning with the centrifuge bucket after a centrifugation operation.
The present invention overcomes the problems of the prior art by providing in various embodiments methods and apparatuses for location of the rotor of a centrifuge, for accurately determining the rotational position of a centrifuge bucket, and for aligning a centrifuge bucket to aid an automated process for removal of samples from the centrifuge bucket.
In one embodiment, a rotor locator for a centrifuge includes first and second locator arms each having a notch. The notches align when the locator arms move between a first position in which the arms are separated, and a second position in which the arms are substantially aligned along one edge. The notches form around a locator pin when the rotator arms move to their second position.
In another embodiment, a centrifuge includes a rotatable centrifuge body with a number of centrifuge buckets and a cover, a drive motor coupled to a rotor shaft to rotate the centrifuge body, and a rotor locator to move the centrifuge body to a known position.
In yet another embodiment, a method for locating a centrifuge body includes centering a rotor shaft of the body along a known center line, aligning the body to a home position, and placing samples in one or more centrifuge buckets. Once the samples have been placed, they are centrifuged. When centrifuging is completed, the method further includes re-centering the rotor shaft along the known center line, re-aligning the centrifuge body to its known home position, and removing the samples.
Other embodiments are described and claimed.